1. Field of the Invention
The present invention relates to an X-ray examination apparatus including a movable table top system and a surrounding X-ray imaging system, both of which are movable by the combined movements of a plurality of carriage means supporting the X-ray imaging system.
In particular, the present invention relates to an X-ray examination apparatus which includes an automatic positioning system for moving an image receptor in the X-ray imaging system along a radiation axis of the X-ray by interlocking the carriage means.
More particularly, the present invention relates to a versatile X-ray examination apparatus which can automatically change between an automatic positioning mode and a manual positioning mode of the image receptor in the imaging system in response to a location of the image receptor against a table top.
2. Discussion of the Background
X-ray examination apparatuses are used both in medicine and industry. In order to simplify the description of the apparatus, the discussion below is directed only toward medical applications.
The X-ray examination apparatus includes a movable table top for supporting a patient being examined and an X-ray source and an imaging receptor mounted on opposite ends of a C- or U-arm carriage means (hereinafter "C-arm") so as to surround the table top.
Usually, an image intensifier (hereinafter "I.I.") is used as the image receptor for detecting X-rays transmitted through a patient'body and for reproducing X-ray images. In a versatile X-ray examination apparatus, the reproduced X-ray images are usually displayed on a monitor, such as a television monitor.
Depending upon the purpose of a diagnostic examination, the radiation axis of the X-ray examination apparatus must be moved in various directions in order to obtain a plurality of X-ray images by intersecting the patient's body in various directions. Changing the intersecting directions is required, in particular, when a contrast medium, such as barium, is used during the examination.
In a conventional X-ray examination apparatus, a patient is required to change his posture in various directions by himself in order to move the contrast medium to a desired position in his body. Moving on the table top is often difficult for elderly or disabled patients.
A versatile X-ray examination apparatus has been developed for avoiding these difficulties for patients. In the versatile X-ray examination apparatus, a patient is supported on a table top and does not move with respect to the table top as both the table top and the imaging system are moved in various directions. The imaging system usually includes an X-ray source and an image receptor which are mounted on opposite ends of a C-arm holder so as to dispose the table top between them.
By combining the respective movements of the table top and the C-arm holder, the versatile X-ray examination apparatus can obtain various X-ray images of the patient's body in various directions without any difficulties for the patient.
However, it is very difficult to manually move the image receptor as close as possible to the patient's body or the table top by interlocking the movements of the table top and the carriage means for the imaging system. Such a manual positioning of the image receptor at a specified closest position to the table top is very important for obtaining a good quality reproduced X-ray image.
It is very difficult to move the image receptor to the best position by a manual operation because the operator sometimes cannot see the position of a detecting surface of the I.I. from his position at a control panel due to the position of the table top or the patient's body. In such a case, the operator is obliged to move the I.I. while estimating the best position.
Some of the I.I.s in conventional versatile X-ray examination apparatuses have touch sensors on the detecting surface for automatically stopping the movement of the I.I. when the detecting surface touches a surface of the table top or the patient body. Even in the versatile X-ray apparatus, the I.I. must be manually moved in a reverse direction after stopping for backing the I.I. to a desired position for obtaining the best magnification of a reproduced X-ray image.
As mentioned above, it is very difficult to place the detecting surface of the I.I. in the conventional versatile X-ray examination apparatus at the best position for obtaining a desired magnification of the X-ray image. Further, the manual operation for positioning the I.I. at a desired position is a time consuming one. Consequently, a patient may feel stressed or fatigued during the preparation time before the actual examination.